Cannulas are one example of microsurgical instruments used in ophthalmic surgical procedures, such as retinal detachment surgery, to aspirate fluids such as blood, aqueous humor, and/or balanced saline solutions (BSS) referred to as infusion fluid. These cannulas are typically connected by tubing to the machine-induced vacuum source and the fluids are collected in a disposable cassette (e.g., at a control console). For ophthalmic surgical procedures, it is important that the cannula tip be specially designed for the delicate eye area. For example, some cannula tips are formed with a soft, compliant tip formed from a transparent soft material (e.g., such as silicone). The soft tip helps prevent damage to the delicate tissue of the eye in the event of physical contact with the eye, typically the retina.
Retinal detachment is a serious eye condition that, if not treated early, may lead to impairment or loss of vision. The retina is a fine layer of nerve cells that covers the inside back portion of the eye. If the retina thins, one or more tears or holes in the retina may result, leading to retinal detachment. Retinal detachment is caused by shrinkage of the vitreous. The vitreous is a clear, gel-like substance that fills the inside of the eye and is firmly attached to the retina especially near the periphery. As the vitreous shrinks, as a result of age, inflammation, injury or near-sightedness, it often separates from the retina and, in some cases, it may pull a piece of the retina away with it, leaving a tear or hole in the retina. If the retina tears or breaks, watery fluid from the vitreous may pass through the hole and flow between the retina and the back wall of the eye producing “subretinal” fluid. Over time, the flow of the vitreous fluid between the retina and the back of the eye separates the retina from the back of the eye and causes it to detach.
Some ophthalmic procedures require a soft-tipped microsurgical instrument that minimizes inadvertent injury to the delicate structures within the eye. During certain ophthalmic procedures (e.g., retinal tear, retinal detachment, and/or vitreoretinal procedures), for example, the tip of a cannula may be used to manipulate the retina, to fill the vitreous cavity with air or gas, and/or more commonly to remove blood, subretinal fluids, or intravitreal fluids. If the flow of vitreous fluid under the retina through retinal breaks or holes has caused the retina to detach, the detached portion of the retina may need to be reattached by draining subretinal fluid from under the retina to allow the retina to be replaced into its anatomically correct position.
During posterior segment surgery, the surgeon typically uses several different instruments throughout the procedure. This frequently requires that these instruments be repeatedly and/or sequentially inserted into and removed out of the incision. To guard against trauma to the incision site from the repeated entry/exit of instruments, surgeons generally insert the instruments through cannulas consisting of a narrow tube with an attached hub. The surgeon typically makes an incision on the eye (e.g., with a trocar through the sclera) and inserts the tube of the cannula through the incision up to the hub, which acts as a stop that prevents the tube from entering the eye completely. Valved cannulas were developed to address the issue of fluids flowing out of the tube when the tube is not connected to an infusion device, or when an instrument is not inserted within the tube because the interior of the eye is pressurized. In some instances, valved cannulas include a slit silicone diaphragm or cap on the outside of the hub. The slit provides an opening into the tube through which the surgical instrument can be inserted. However, a soft-tipped cannula may be insufficiently rigid to effectively open the slit without the application of undue pressure against the cannula. Thus, surgeons frequently need to use a more rigid instrument to open the slit before advancing a conventional soft-tipped cannula through the slit into the cannula.
Accordingly, there exists a need for an improved instrument configured for “soft-tipped” use while also capable of passage through a valved cannula. The systems and methods disclosed herein overcome one or more of the deficiencies of the prior art.